Contactor base for electric lamps, tubes, and the like



con-uc'roa BASE FOR ELECTRIQ LAMPS, TUBES, AND THE LIKE Jan 2, 1940 c.w. HALLER 2 Sheets-Sheet 1 Filed April 10; 1939 CYRUS W HALLER,

INVENTOR. M

ATTORNEY.

Jan. 2', 1940. I c. w. HALLER 2,185,981

CONTACTOR BASE FOR ELECTRIC LAMPS, TUBES, AND THE LIKE Filed April 1'011939 2 shedshea 2 CYRUS W. HALLER,

' INVENTOR.

ATTORNEY.

' rhesus it 2, 1940 a "new con'rsc'ron BASE son. Ema-mic LAMPS, 'ronns,AND 'rnn LIKE 'Cyrus W. Haller, Marblehead, Mass, assignor to HygradeSylvania Corporation, Salem, Mass., a corporation of MassachusettsApplication April 10,1939, Serial No. 287,025

6 Claims. (cl- 178-32) This invention relates to contactor bases andmore particularly to bases for electric lamps, radio tubes and similardevices.

A principal object of the invention is the pro- 6 vision, for suchdevices, of a screw base in which an insulating cup is the main supportof the base and carries the necessary metal contact pieces intimatelybonded to its surface.

Heretofore in the manufacture of incandescent 10 electric-lamps of theconventional screw-base y the base consists of a previously threadedmetal shell insulatingly carrying at the bottom a metal contact button.This button is usually insulated from the shell by arelatively shallowlls vltreous cup-like ring which is fused to the shell and to thecontact button. The'flnished'base is then usually cemented to the lampbulb by a relatively narrow ring of cement, thus leaving the greaterpart of the inner face of the shell exposed. when such a base isemployed in connection with a fused lead-in wire there is considerabledanger of the gases and vapor released by the blowing of the fuse,causing a destructive are within the base. There is disclosed in' U. S.Patent No. 35 2,141,146, issued December 20, 1938, to R. M.

Zabel, a method of protecting the normally exposed inner face of theshell by extendingthe glass skirt upwardly. Accordingly, another objectof the present invention isto provide an imgar-proved method ofinsulating substantially the entire inner face of the usual threadedmetal con-- tactor base, while'atthe same time improving the mechanicalconstruction and appearance of the base.

'llhe improvement in mechanical construction is obtained by using theinsulation for the interior of the shell as the main supporting memberof the base. This is done bymolding a cup-shaped insulating member tosubstantially the shape of %-the finished base and intimately bonding toits surface metal contact pieces thin enough to conform closely to saidsurface. This canbe accomplished by molding the insulation and the metalpieces simultaneously in a single unit as describedgg hereinafter: bymolding the insulating cup and then depositing the metal on it byelectrolysis orby spraying; or by any similar process.

a construction permits the use of a thinbase 0111mm 5.

cause. the dimensions are fixed by the molding process.

A further object of the invention is the provision of a lamp or tubebase with a threaded metal contact supported-or embedded in insulat- 6ing metarials which have hitherto not been found practicable for thispurpose. .Among such mate! rials may be mentioned particularly, theplastics of the thermosetting type, such as Bakelite and similarphenolic condensation products. Such in- 10' sulators will not chip, orcrack, and are capable of more accurate molding, than is the usual glassinsulator.

A feature of-the invention is a base in which can readily beincorporated continuous, discon- 16' tinuous or special threads foridentification or theft-proof purposes.

Other features and advantages not specifically enumerated will beapparent after a consideration of the following detailed descriptionsand the appended claims. i

While the invention will be described herein in connection with themanufacture of a screw-base for lamps, it will be understood that thebase is equally well adaptable to radio tubes, resistors, fuses, plugsand similar electric devices which are designed to be connected into theconventional screw-threaded lamp socket or the like. Accordingly in thedrawings:

Figure 1 is a vertical cross-sectional view of a typical molding devicefor carrying out the method according to the invention.

. Figure 2 is another view of the apparatusof Figure 1. showing themolding die in its molding 45 position. I

Figure 3 is a partial sectional view of a typical form of thin walledmetal shell that is used with the molding device of Figures 1 and 2.

Figure 4 is a bottom ,plan view of Figure 3. Y 50 Figure 5 shows oneform of base according to the invention. h

' Figure 6 isa perspective view of the particular type of shell blankthat is used in producin'g'the PATENT OFFICE Figure 7 shows a type ofbase produced using the shell blank of Figures 2 and 3.

Figure 8 shows a modified form of base according to the invention, withdiscontinuous screw threads.

Figure 9 shows a bottom plan view of Figure 8.

Figure 10 shows a further modification of the' base.

Figure 11 is a view of a modified form of die that may be used in themanufacture of bases for certain types of mechanically based bulbs.

Figure 12 is an exploded view of a bulb and its co-operating base formedin accordance with the invention and using the die of Figure 11.

Figure 13 shows a base similar to the base of Figures 1 and 2 andprovided with a locking recess therein.

Figure 14 shows a modification of the base of Figure 5.

Figure 15 shows a modification of the shell blank of Figure 3. Referringto Figures 1 and 2, the numeral I represents a mold made of any suitablematerial and is provided with a substantially cylindrical smoothfacedmold cavity 2, the bottom of which is recessed as indicated by thenumeral 3, and the cylindrical wall of which is provided with a roundscrew-thread I. Preferably the thread 4 is designed so that when thebase is formed as described below, the base threads are of the pitch andshape ordinarily employed on incandescent lamp bases. Themold I, may beof one piece but is preferably of two pieces suitably fastened together.Co--operating with the mold I, is a specially shaped die or plungerhaving its forward end tapered as indicated bynumeral 6, and terminatingin a cylindrical tip I. The main body portion 8 of the die is preferablycylindrical and joins a'flared portion 9, which in turn joins ashouldered portion l 0. The cylindrical portion 8 is of smaller diameterthan the inside diameter of the mold cavity, the difference in diametersdepending upon the thickness of the insulation wall desired in thefinished base.

Any well-known form of heating means (not' shown) may be provided forbringing the mold to the proper temperature for setting. For Bakelitethis temperature is about 350 C.

In order to form the base, there is positioned within the mold cavity athin-walled metal shell or cup I I (Figs. 3 and 4) of brass or othersuitable metal such as is ordinarily employed in the manufacture ofscrew-bases for incandescent lamps. After the metal shellis placed inthe mold, a cylindrical pellet I2 of a suitable heat-hardening,

often called thermosetting, plastic insulation material may be employed.As examples of materials that are useful for this purpose may bementioned, powdered Bakelite or similar condensation product eitheralone or mixed with 'a ceramic powder, asbestos powder or the like. Ifdesired the pellet may consist entirely of a suitable compressedpowdered ceramic such as porcelain, Isolantite or the like, ,towhich'has been added a heat-hardening, often called thermosetting,binder which becomes plastic when subjected to the molding temperatureand pressure.- Preferably, although not necessarily, the pellet isprovided with a central opening l3, and the bottom face of the pellet isrecessed at II to receive the usual eyeletted metal inset 20. When themold is heated to the proper'temperature the die is moved downwardly andsubjected to suitable pressure to cause the pellet to become plastic andfill the space between the die and the inner face of shell II. At thesame time. the die forces'the button I5 down against the bottom ofrecess 3, I

breaking the ribs 49, which join the eyelet button to the remainder ofthe metal shell, and also forces a quantity of the plastic insulationthroughthe circular opening I6 in shell II causing this insulation toassume the shape of the said recess as shown clearly in Figure 2. Thepellet is so proportioned in volume that when the die reaches itslower-most position as shown in Figure2, there is a suflicient quantityof the plastic insulation to provide the desired thickness to the wallII. It will be understood that when the die first engages the pellet itcauses the shell I I to be firmly held against the portion I8 of themold so that further downward movement of the die forces the plasticinsulation upwardly between the die face and the shell. Furthermore theclose flt between the shoulder I on the die, and the cylindricalwall-portion I9 of the mold, prevents the plastic insulation from beingforced upwardly beyond the rim of shell II.

I have found that if the shell I I is of sufficiently thin metal stock,the die pressure is transmitted through the insulation I! to cause thewall of .the shell to conform itself to the threaded surface of themold, consequently the shell is formed with the screw-thread at the sametime that a corresponding thread in the insulating wall I! is formed.Preferably the die tip I is of about the same length as the eyelet 20 sothat the die engages the rim of the eyelet. and prevents the plasticinsulation from, flowing through the eyelet. When the base has beenformed as described, the die is removed and the insulation is allowed toharden whereupon the two halves of the mold may be opened and thefinished base removed. The base will then be found toconsist of aninternal cup-like insulating shell the outer surface of which isappropriately threaded and the correspondingly threaded metal shell IIis in intimate bonding contact with the insulating shell over its entirethreaded area. The contact button I is also bonded to the insulatingshell and the eyelet 20 is accurately centered on the vertical axis ofthe base. ,Also the insulating shell is formed with a smooth conicallyinclined wall 2| communicating with the eyelet, and the slant of wall 2|may be such as to facilitate the insertion of the usual lead-in wirethrough the eyelet thus enabling the base to be conveniently used on anywell-known type of automatic machine for applying the base to a'suitablelamp or tube bulb.

From the foregoing it will be seen that by choosing a suitableinsulation material for the pellet I3, it is possible to impart a verypleasing appearance to the finished base as the insulation may be madein any desired color or combination of colors. Furthermore, it ispossible to form .the base with greater accuracy than is possible wherea pre-threaded metal shell is employed and fastened to the eyelettedbutton by the usual shallow glass ring. It is also possible by thismethod of base formation to employ insulating materials which are notadaptable to the usual methods of forming bases. Thus it is possible toproduce a base wherein-the exteriorly exposed portion of the insulationis substantially chipproof. Furthermore, the portion 22, being integralwith the wall portion II provides a rigid support for the shell I I,both against vertical as well as against radial crushing. It will. beunderstood.

'of course, thai if desired the recess 3 in the mold may be made as deepas is found necessary to provide the requisite spacing between the lowerrim of shell I I and the metal button I5.

shell is formed with a series of thread-sectors 23 on one side and asimilar series of thread-sectors 24 on the opposite side, it beingunderstood that the sectors are in eifect sectors of what wouldotherwise be a single continuous thread such as is shown, for example,in- Figs. 2 and 14, the intermediate unthreaded portions of both themetal 25 and the insulator shell 26 being cylindrical. The eyelettedmetal contact button 21, is integrally bonded to the extension, of theinsulator shell as described in connection with Figs. '1

and2.

If desired, the thread-sectors may be so formed during the moldingprocess that the base is capable of being turned readily in onedirection into the usual threaded socket, but is incapable of beingturned in the opposite direction. Thus, as shown in Fig. 10, the threadsectorsare formed with pointed inclined ends 29, 30, which do notinterfere with the rotation of the base into the usual threaded socket,but which lock against the socket threads when the base is turned toremove it from the socket. -It will be understood, of course, that thebase may be molded with any other form of mutilated thread, and whilethe sectors may be formed;

In Figure 2, the ribs 49, which unite the eyeletted button to the mainmetal shell of Figs. 3 and 4, have been broken by the molding process toseparate the eyeletted contact button and the cylindrical metal shell.The portion of the ribs remaining with the contact button will be setinto the molded insulation shell, serving as addi-, tional anchors forthe contact button.

Instead of employing a metal shell in the form of a complete cylinder,as shown in Figs. 3 and 4, the shell may be made in skeleton form, suchas shown in Fig. 6 comprising a rim 34 formed with a set of spacedstrips 35. The manner of. using this skeleton shell is the same as thatdescribed in connection with Figs. 1 and 2, and the finished base thusproduced is shown in Fig. 5. In this embodiment the vertical strips 35are imbedded in the insulation shell 36 and each strip is molded at thesame time the insulation shell is formed so that both the shell and thestrips have the required threads therein. It will be obvious thatinstead of employing the strips 35, as integral extensions of the rim34, the stripsalone may be employed and held in the mold in any suitablemanner in circumferentially spaced relation so that when the insulationpellet is subjected to heat and pressure the strips imbed themselves inthe molded insulation shell, and are flush with the outer face of theinsulation shell.

In the foregoing embodiments of the invention the insulator portions 2 i26 etc., are molded with a substantially smooth inner surface and thebases are capable ofbeing fastened to the lamp or bulb by a bondingcement or the like in the usual manner. However, the process is alsoapplicable to the control-of the configuration of the internal surfaceas well as the external surface Figs. 1 and 2.

or the insulatorshell. For example, in lamps-of these-calledmechanically based type, the portion of the lamp bulb adjacent the sealmay be provided with integral screw threads, depressions,

beads or the like which are' arranged to' interlock 1 with correspondingthreads, depressions, beads, etc., on the internal surface of the metalshell base. Examples of such mechanically based lamps areillustrated inU. S. Patent No. 2,028,- 884, issued January 28, 1936 to R. B. Thomas.

vReferring to Figs. 11 and 12, a description will be given of the mannerof applying the process to the manufacture of one illustrative form ofme: chanically based bulb.

Asshown in Fig. 12, the bulb 3'l has its butt portion-l8 provided withraised thread sectors, 39 preferably, although not necessarily, of theconfiguration shown. I Whilethe drawings show only one set of threadsectors, it will be understood that a' similar set or sets maybeprovided around the periphery of the butt 38 and these sectors may, ifdesired, be molded at or during the 'operationof sealing the reentrantstem 40 into the bulb. The base which is shown in section in .the lowerpart of Fig. 12 may besimilar to the bases shown in Figs. 5, 7, 9, 10,l3, l4, and may be manufactured in accordance with the process describedin detail in connection with The only difference is that in place of thesmooth-faced die 8, there is em-' ployed a die such as shown in Figure11 which has its cylindrical face provided with recessed thread sectorsll to correspond to the thread sectors 39 on the lamp butt 38, thusforming the insulator shell 42 with correspondingly raised sectors 13'.The base may then be threaded on to the butt 38 and fastened in-anysuitable manner. Thus the lead-in wire N may be bent back upon itselfand the free end soldered to the rim of the metal shell 45. It will beobvious that instead of molding the internal face of the insulator shell42 with thread sectors the die may have its cylindrical face formed witha continuous recessed plural turn screw-thread and the butt 38 maylikewise be provided with a continuous plural turn raised screw-threadwith a transverse slot to receive the bent back lead-in wire 44 inthemanner illustrated, for example, in Patent No. 1,650,289 to J. B.McGinley. In carrying out the process in connection with the type ofbase shown in Figure 12, it may be necessary to make the die in sectorswhich may be collapsed or removed in order to allow for the removal ofthe finished base from the die. It will be understood, of course, thatthe embodiment of Figure 12 is merely illustrative of one particularconfiguration for the internal wall of the insulator shell.

'In certain cases, it is desirable to provide a bulb with a base that iscapable of receiving a locking member when the bulb is inserted in thereceptacle. Thus, as shown in Figure 13, the base which may be of any ofthe forms disclosed in the preceding figures has its external threadedsurface molded with a recess or slot 46 to receive a locking screw orprojection (not shown) for preventing the bulb being removed from its'Instead of employing a cylindrical shell or skeleton shell (Figure 5),the side contact of the base may consist of a simple strip of metal 41,which may be held in the mold in any convenient manner so that when thedie forces the plastic insulation to shape, the strip will be embeddedin the plastic and the base will consist for the most part of anexternally threaded shell 48, of the insulation having embedded in itsouter face the correspondingly threaded metal strip 41. Instead ofemploying a seamless metal shell ll (Figures 3 and 4), for forming thebase, this shell may be made from a strip of the metal having its edgesoverlapped as indicated in Figure 15.

As an alternative method, the metal shell ll may be omitted and afterthe insulation is molded to the desired formation with the button oreyelet 20 thereon, as described in connection with Figures 1 and 2, thedesired portion or por-- tions of the outer surface of the moldedinsulator shell may be provided with a coating of conductive material asby spraying, dipping, electrolytic deposition, painting or the like.

It will be understood that the invention is not limited to the use ofmetal sheet stock for the shells H, 25, 34, and that the' metal mesh,perforated metal or any form of foraminous metal stock may be employed.Other changes and modifications may be made in the embodimentsdisclosed, without departing from the spirit and scope of the invention.

This application is in part a continuation of my application Serial No.52,286, filed November 30, 1935, and issued May 9, 1939, as U. S. PatentNo. 2,158,044. I

What I claim is:

1. A contactor base for lamps and the like, said base comprising a mainhollow cup-like thinwalled member of thermally-set insulation, thecylindrical portion of said member containing screw threads on thecylindrical portion of its external surface, a correspondingly threadedthin metal cylindrical shellintegrally bonded to said surface, saidmetal shell extending to but not beyond thetop of the cup-like memberand extending toward but spaced from the bottom of said cup-like member,an eyeletted flat metal contact disk integrally bonded to the bottom ofsaid cup-like insulating shell and out of contact with said metal shell,the eyelet in said disk being in register with a small hole in thebottom of the insulating shell and being flared outward in theinsulating shell for bonding purposes, the eyelet extending upward intothe circumference of the hole, the disk having small ribs extending fromits circumference upward into the insulating cup for bonding purposes,the cup-like shell of insulation being flared outward at its top to meetthe top of the cylindrical metal shell.

2. The combination of claim 1, in which the metal shell is too thin tobe rigidly self-supporting of itself, the insulating cup combining withit to form an integrally self-supporting structure in combination.

3. The combination of claim 1, in which the metal shell is too thin tobe rigidly self-supporting of itself, the insulating cup combining withit to form an integrally self-supporting structure in combination, andin which the combined structure is integrally slotted transversely ofits threads. i

4. The combination of claim 1, in which the metal shell is too thin tobe rigidly self-supporting of itself, the insulating cup combining withit to form an integrally self-supporting structure in combination, andthe combined structure is integrally slotted transversely of thethreads, and in which the insulating cup-like member bears parts ofthreads on its interior surface, the parts of threads being arrangedto,fit corresponding parts of threads on the neck of an incandescentlamp bulb.

5. The combination of claim 1, in which th main hollow thin-walledmember of thermallyset insulation has its hollow interior in the form]of a cylinder terminating at its bottom in a cone providing a slantedsurface to facilitate the insulation of a lamp lead-in, wire. 6. A metalblank for use in lamp basemanufacture comprising a thin" walledcylindrical metal shell terminating ina substantially flat v surface atone end of the cylinder, the other end being open to form a cup-likeshell, the bottom-

